Coke drum drill stem alignment device
BACKGROUND OF THE INVENTION 
     This invention relates to methods and apparatus for use in connection with the preparation of coke from crude petroleum products. 
     A &#34;delay coker&#34; is an apparatus for the preparation of coke from the heaviest portion of crude oil (commonly referred to as &#34;bunker&#34; fuel). The crude is generally heated to a temperature of about 800-900° C. and then fed into the bottom of a coke drum. The coke drum has a diameter on the order of 25 feet and may be 80-90 feet high. At an elevated pressure (e.g., 30 pounds or more), the heated crude is thermally decomposed to leave a coke residue. During the thermal decomposition, lighter products such as hydrocarbons gases, gasoline and jet fuel, are recovered from the top of the coke drum. The decomposition process takes on the order of 16-20 hours to complete. 
     The solid residue is treated with steam to remove any entrained volatile hydrocarbons. The residue is then cooled down with water. Finally, the coke drum is opened at both the top and the bottom, and the solid product is drilled out for recovery. A typical drilling procedure employs a rotating high pressure water drill (for example, using 3000 lb/in 2  pressure). 
     It has heretofore been necessary after lowering the stem of the drilling device into the drum to manually mount the drill in position, for example using some type of collar means. In one arrangement, a two-piece hinged collar having a generally circular shape was used to align and mount the drill stem. The collar was hoisted onto the drum in an open position, after which the two generally semicircular halves of the collar connected at one end were manually engaged around the drill by swinging them together. The collar was finally clamped to a flange on the top of the coke drum to fix the drill stem into position. The two halves of the collar were suitably joined together at one end by pins, so that the arms could be swung away from the position of engagement when not in use. 
     A principal disadvantage of the known arrangements for aligning and mounting the drill stem is the need for manual adjustment of the collar. Because of the heat generated in the coke drum, the top flange of the coke drum and the collar itself could be quite hot. Moreover, during the engagement and clamping operations, workers could be exposed to steam and residual heated hydrocarbons escaping from the steam-treated solid materials in the drum. In addition, movement of the drill stem could cause the collar to slide out of engagement position or off the top flange of the coke drum if it were not already clamped securely in place. 
     Accordingly, it is an object of the present invention to provide apparatus and methods for bringing the drill stem into engagement and proper alignment with the top end of a coke drum, which apparatus and methods would eliminate the need for direct operator contact with the coke drum and/or associated elements. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, apparatus and methods are provided for alignment and mounting of the drill stem without direct operator contact. The drill stem is provided in the vicinity of the cutting tool with a drill stem guide carried on a slidably mounted plate. A flange on the drill stem is provided to prevent movement of the plate below a particular point. In a preferred embodiment, automatic clamping means are provided to attach the plate to an end flange on the coke drum when the drill stem guide has been lowered into the coke drum a sufficient distance to permit disengagement of the flange on the drill stem from connecting elements of the clamping means provided on an upper surface of the plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates an embodiment of the apparatus of the invention means in schematic form, in conjunction with a corresponding coke drum; 
     FIG. 2 is a side cross-section view of an embodiment of the inventive apparatus; and 
     FIG. 3 is a top perspective view of an embodiment of the inventive apparatus illustrating the rotational stops. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a coke drum 1 is illustrated with an upper lid 2, a lower lid 3, a feed inlet 4 for introduction of crude and a feed line 5. An aperture 6 with an end flange 7 is provided in the upper lid 2. A fluid source 8 is provided at one end of the drill stem 9; a cutting tool 10 is provided at a second, opposite end of the drill stem 9. The alignment device of the invention (generally depicted in FIG. 1 at 11) is shown for purposes of clarity as comprising a single clamping device (generally depicted at 12) and a first rotational stop 20 adapted to engage a second rotational stop 21, the latter being provided on the upper lid 2 of the coke drum 1, laterally displaced from the aperture 6 and the end flange 7. 
     FIG. 2 illustrates a preferred embodiment of the inventive apparatus, comprising a pair of clamping devices 12. A flange 13 is mounted on the drill stem 4 between the cutting tool 10 and the fluid inlet 8. A generally circular plate 14 is mounted slidably on the drill stem 9 between the flange 13 and the fluid inlet 8, and is supported by the flange 13 when the drill stem is not in engagement with the coke drum (the situation depicted in FIG. 1). Preferably (as illustrated in FIG. 3), a substantial portion of the surface area of the plate 14 comprises webbed metal to permit escape of steam. A guide structure 15 associated with plate 14 is provided to facilitate alignment of the drill stem 9 (and cutting tool 10) in the coke drum 1. 
     The guide structure 15 is suitably mounted on the underside of the plate 14, facing the flange 13, near the periphery of the plate 14 and extends generally normally from the plate 14. The guide structure 15 is designed so as to be received in the aperture 6 of the coke drum 1. In particular, the coke drum 1 is provided with a generally cylindrical passage which is aligned with the longitudinal axis of the drill stem 9 and of sufficient diameter to receive the guide structure 15. In a preferred embodiment, the guide structure 15 comprises a plurality of guide legs 16 attached at one end to a face of the plate, thereby forming a circular pattern. The opposite ends of the guide legs 16 may then suitably be attached to a generally circular nose piece 17 with a diameter less than that of the plate 14 or the aperture 6. In a preferred embodiment, this nose piece 17 is formed of tubing with a roughly circular cross-section. This arrangement facilitates moving the guide structure 11 into the aperture 6 and reduces damage to the internal lining (i.e., cladding) of the coke drum 1. 
     The cutting tool 10 at the end of the drill stem 9 is typically also of a generally cylindrical shape and has an outside diameter which is less than the diameter of the nose piece 17. Thus, when the alignment device 11 is lowered into the aperture 6 in the upper portion of the coke drum 1, the guide structure 11 serves to align the device in a manner such that the concentrically mounted cutting tool 10 is in the appropriate position for operative insertion into the coke drum 1 (for example, into a nozzle located in the lower portion of the aperture 6). In addition, because the diameter of the cutting tool 10 is less than that of the nose piece 17, it is possible to move the drill stem 9 relative to the guide structure 11 such that the cutting tool 10 passes through the nose piece 17. 
     In accordance with a further embodiment of the present invention as illustrated in FIG. 3, the apparatus is provided with a first rotation stop 20 extending radially outwardly therefrom, for example, from the plate 14, to prevent rotation of the alignment device induced by rotation of the drill stem 9. A corresponding second rotation stop 21 is provided on the upper surface of the coke drum 1 (for example, on upper lid 2) so as to contact the first rotation stop 20 at a particular position in the rotation of the device. In this manner, rotation of the device is limited. In one embodiment, the first rotation stop 20 may comprise an arm projecting out from the plate 13, and the second rotation stop 21 may comprise an arm projecting up from the top surface of the coke drum 1 and laterally displaced from the end flange 7. 
     In accordance with a preferred embodiment of the invention, the plate 14 is further provided with at least one, and preferably several, boreholes 30 extending through the plate 14 at a location aligned with a portion of the flange 13. A pin 31 is slidably positioned in each borehole 30; a head at the upper portion of the pin 31 is designed to retain the pin 31 in the borehole 30. A generally C-shaped clamp 32 is positioned generally radially outwardly from the plate 14. The clamp 32 has an upper arm 33 pivotally connected to the top surface of the plate 14, a lower arm 34 extending beneath the bottom surface of the plate 14 when the clamp 32 is in an engaged position (as illustrated in FIG. 2), and a connecting arm 35 extending past the outer periphery of the plate 14. A lever 36 is pivotally mounted by its midportion to the top surface of the plate 14. The inner end 37 of the lever 36 is positioned so as to cover the head of the pin 31, whereas the outer end 38 is positioned so as to engage as a cam the free end of the upper arm 33 of the locking clamp 32. The arrangement is such that when the flange 13 is urged against the lower end of pin 31, the head of the pin 31 causes the lever 36 to pivot; as the outer end 38 of the lever 6 pivots down, it causes the upper arm 33 of the C-shaped clamp 32 to swing the lower arm 34 radially outwardly and thus, out of the engaged position (as illustrated in FIG. 1). 
     In general, end flange 7 is positioned at the upper end of the coke drum 1 surrounding the aperture 6. The outside diameter of the end flange 7 is approximately the same as that of the plate 14, and the thickness of the end flange 7 sufficiently small so that the lower arm 34 of the locking clamp 32 may engage the lower surface of the end flange 7 when it is swung into engagement position (as illustrated in FIG. 2). 
     In operation, the plate 14 is directly or indirectly carried on the flange 13 positioned on the drill stem 9. When the plate 14 is lowered into abutment with the upper end flange 7 of the coke drum 1, the drill stem 9 is aligned with the assistance of the guide structure 11. The drill stem 9 is then lowered through the guide structure 11 and into the coke drum 1, thereby also bringing the flange 13 on the drill stem out of contact (direct or indirect) with the plate 14. Once the plate 14 is in abutment with the coke drum end flange 7, the device may be fixed in position (for example, by associated clamp means 12 or by external clamps separately provided). 
     With the preferred embodiment including generally C-shaped clamp means 32 as described previously, when the flange 13 on the drill stem 9 is moved out of contact with the bottom end of pin 31, the pin 31 in aperture 30 of plate 14 no longer remains in the extended position illustrated in FIG. 1 and the head of the pin 31 does not urge inner end 37 of lever 36 upward. Therefore, the inner end 37 of the lever 36 pivots down while the outer end 38 of the lever 36 pivots up, whereby the upper portion 33 of clamp 32 follows to move the lower portion 34 of clamp 32 below the end flange 7 on the coke drum 1 (i.e., the engagement position illustrated in FIG. 2). 
     From the foregoing description, one skilled in the art can readily ascertain the essential characteristics of the invention and, without departing from the spirit and scope thereof, can adapt the invention to various usages and conditions. Changes in form and substitution of equivalents are contemplated as circumstances may suggest or render expedient, and although specific terms have been employed herein, they are intended in a descriptive sense and not for purposes of limitation.